Magnetic resonance imaging compatible catheter

ABSTRACT

A method, consisting of passing a cylindrical carbon fiber through a press so as to produce a flat ribbon. The method further includes weaving multiple strands of the flat ribbon together to create a cylindrical braid.

FIELD OF THE INVENTION

The present invention relates generally to invasive probes, andspecifically to producing a magnetic resonance imaging compatiblecatheter.

BACKGROUND

A wide range of medical procedures involve placing objects, such assensors, tubes, catheters, dispensing devices, and implants, within thebody. When placing a medical probe fitted with position sensors withinthe body, a reference image of the body cavity being treated istypically presented on a display. The reference image assists a medicalprofessional in positioning the probe to the appropriate location(s).

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a method, including,

passing a cylindrical carbon fiber through a press so as to produce aflat ribbon; and

weaving multiple strands of the flat ribbon together to create acylindrical braid.

Typically, the press includes a roller press. In one embodiment thecarbon fiber has a diameter no greater than 500 μm.

In a disclosed embodiment the method includes repeating passing thecylindrical carbon fiber through the press one or more times until theflat ribbon meets defined dimensional specifications. Typically, thedimensional specifications define a rectangle having a width no greaterthan 500 μm, and a thickness no greater than 500 μm.

In an alternative embodiment the cylindrical braid is flexible.Typically, the method includes cutting the flexible cylindrical braid toa pre-defined cut length, thereby creating a section; covering thesection with a flexible biocompatible sheath; and positioning one ormore functional elements within the cut length of the braid, therebyproducing a magnetic resonance imaging compatible medical probe.

Each of the one or more functional elements may be selected from a listconsisting of an electrode, a position sensor, a force sensor, cablingand tubing. The magnetic resonance imaging compatible probe typicallyconsists of only non-magnetic materials.

There is further provided, according to an embodiment of the presentinvention, a medical probe, which has proximal and distal ends andincludes:

a flexible cylindrical braid woven from multiple strands of a flatcarbon ribbon;

a flexible biocompatible sheath that is formed over the braid; and

one or more functional elements running within the braid between theproximal and the distal end of the probe.

Typically, the probe includes only non-magnetic materials.

Each of the one or more functional elements may be selected from a listconsisting of an electrode, a position sensor, a force sensor, cablingand tubing. Typically, the flat carbon ribbon has dimensionalspecifications defining a rectangle having a width no greater than 500μm, and a thickness no greater than 500 μm.

There is further provided, according to an embodiment of the presentinvention, a method, including:

weaving a flexible cylindrical braid from multiple strands of a flatcarbon ribbon;

forming a flexible biocompatible sheath over the braid so as to producea probe having proximal and distal ends; and

running one or more functional elements within the braid between theproximal and the distal ends of the probe.

There is further provided, according to an embodiment of the presentinvention, a method, including:

forming a flexible biocompatible sheath over a flexible cylindricalbraid woven from multiple strands of a flat carbon ribbon, so as toproduce a probe having proximal and distal ends; and

running one or more functional elements within the braid between theproximal and the distal ends of the probe.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1A is a pictorial illustration of an apparatus for producing acarbon ribbon, in accordance with an embodiment of the presentinvention;

FIG. 1B is a pictorial illustration of a braiding apparatus used forproducing a braid of the carbon ribbon, in accordance with an embodimentof the present invention;

FIG. 1C is a magnified pictorial illustration of the braid produced bythe braiding apparatus, in accordance with an embodiment of the presentinvention;

FIG. 2 is a flow diagram that schematically illustrates a method ofproducing a magnetic resonance imaging (MRI) compatible probe, inaccordance with an embodiment of the present invention; and

FIG. 3 is a schematic detail view showing a distal end of theMRI-compatible probe, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

During some medical procedures, magnetic resonance imaging (MRI) is usedto assist in visualizing detailed internal structures of the body. Toproduce an image using MRI, a radio frequency transmitter in an MRIsystem transmits an electromagnetic field. In response to theelectromagnetic field, cells in the body transmit electromagneticsignals, which are detected by a scanner. The MRI image is then producedbased on the received electromagnetic signals.

Since MRI uses strong magnetic fields, any magnetic material in the areabeing visualized may distort the MRI image. In some instances, exposinga magnetic object within the body to the MRI's strong magnetic field maycause a trauma to the patient due to movement of the magnetic objectexposed to the magnetic field.

Medical probes, such as catheters, commonly contain a braided steelreinforcing layer for mechanical strength. This sort of steel layer,however, may create problematic effects when exposed to the strongmagnetic field from the MRI system as described supra.

Embodiments of the present invention provide a method and apparatus forproducing a carbon ribbon, which when braided, can be used to produce amedical probe with a cylindrical carbon braid as reinforcement. In someembodiments, a cylindrical carbon fiber is conveyed through a press suchas a roller press, producing a flat, thin carbon ribbon. The ribbon isthen woven into a cylindrical braid, which can be used as areinforcement layer for a carbon-braided probe.

Carbon-braided probes produced using embodiments of the presentinvention are typically comparable in both strength and flexibility tosteel-braided probes, and are unaffected by the MRI's magnetic field.Furthermore, a carbon-braided probe can be used in other applications,in addition to procedures using MRI. For example, in multi-catheterprocedures, the non-magnetic carbon braid in the catheter may be helpfulin reducing magnetic field disturbance, which can otherwise affectposition and force measurements made by other catheters.

System Description

FIG. 1A is a pictorial illustration of an apparatus 20 for producing acarbon ribbon 36, in accordance with an embodiment of the presentinvention. An operator 24 inserts a cylindrical carbon fiber 26 into aroller press 28, and rotates a handle 30 to advance the carbon fiberthrough the roller press. In some embodiments, carbon fiber 26 may havea diameter between approximately 50 μm and approximately 500 μm.

Roller press 28 comprises two rollers 32, handle 30 and a pressure dial34. Rotating pressure dial 34 increases or decreases the distancebetween the two rollers. Handle 30 is coupled to one or both of rollers32. Operator 24 rotating handle 30 (counter-clockwise, in the exampleshown in FIG. 1A) conveys the carbon fiber between the two rollers,thereby producing flat, thin carbon ribbon 36. Alternatively, rollerpress 28 may include a motor coupled to one or both of rollers 32 inorder to convey carbon fiber 26 between the two rollers. Using thecarbon ribbon whose dimensions are described supra, the dimensionalspecifications of ribbon 38 produced by roller press 28 has a widthbetween 50 μm and 500 μm, and a thickness between 50 μm and 500 μm. Insome embodiments, operator 24 may insert multiple carbon fibers 26simultaneously into roller press 28 thereby producing multiple flatcarbon ribbons 36.

FIG. 1B is a pictorial illustration of a braiding apparatus 38, and FIG.1C is a magnified pictorial illustration of a braid produced by thebraiding apparatus, in accordance with embodiments of the presentinvention. Braiding apparatus 38 is configured to create a cylindricalcarbon braid 22 from ribbon 36. As a rotating wheel 40 conveys aflexible plastic tubing 42 through the braiding machine, a braidingmechanism 44 conveys multiple ribbons 36 from multiple spools 46, andweaves braid 48 (FIG. 1C) surrounding the plastic tubing, therebyproducing cylindrical carbon braid 22.

Producing an MRI-Compatible Catheter

FIG. 2 is a flow diagram that schematically illustrates a method ofproducing a magnetic resonance imaging (MRI) compatible probe inaccordance with an embodiment of the present invention. In an initialstep 50, operator 24 defines a range of dimensional specifications(i.e., length and width) for carbon ribbon 36. The ranges are typicallybased on the specifications of carbon ribbon 36, which may includeribbons of different dimensions. It will be appreciated that one ofordinary skill in the art may determine suitable dimensional ranges forthe ribbon without undue experimentation.

In a compression step 51, operator 24 inserts cylindrical carbon fiber26 into roller press 28, where rollers 32 compress the carbon fiber,thereby creating carbon ribbon 36. In a comparison step 52, if ribbon 36does not meet the dimensional specifications defined in step 50 (i.e.,width and thickness), then the method returns to step 51. Typically,several passes through press 28 may be required to meet the defineddimensional specifications.

If, however, ribbon 36 meets the defined dimensional specifications,then in a weaving step 54, operator 24 loads the ribbon to spools 46 ofbraiding apparatus 38, which then weaves the ribbon into cylindricalcarbon braid 22. In a first probe producing step 56, operator 24 cutsbraid 22 to a pre-defined cut length to create a section of the braidand covers the section with a flexible, insulating, biocompatiblematerial (also referred to herein as a sheath). Finally, in a secondprobe producing step 58, operator 24 positions functional elements, suchas cabling and/or tubing, within the braid, thereby producing anMRI-compatible probe, where the functional elements typically runbetween proximal and distal ends of the probe.

FIG. 3 is a schematic side view of an MRI-compatible probe 60, inaccordance with an embodiment of the present invention. Specifically,FIG. 3 shows functional elements of probe 60 used in creating a map ofcardiac electrical activity. An electrode 64 at a distal tip 66 of theprobe senses electrical signals in cardiac tissue. Alternatively,multiple electrodes (not shown) along the length of the probe may beused for this purpose. Electrode 64 is typically made of a metallicmaterial, such as a platinum/iridium alloy or another suitable material.

A position sensor 68 generates a signal that is indicative of thelocation coordinates of distal tip 66. Position sensor may comprise anelectrode, wherein impedances between the electrode and additionalelectrodes positioned outside a patient's body are measured to determinethe position of the electrode. In alternative embodiments, positionsensor 68 may comprise a tri-coil position sensor (for example, as isimplemented in the CARTO™ system produced by Biosense Webster, Inc.,Diamond Bar, Calif.) or an ultrasonic position sensor. Although FIG. 3shows a probe with a single position sensor, embodiments of the presentinvention may utilize probes with more than one position sensors.

A force sensor 70 senses contact between distal tip 66 and endocardialtissue, by generating a signal that is indicative of the pressureexerted by distal tip 66 on the tissue.

Probe 60 is covered by a biocompatible, flexible sheath 72. Sheath 72 isshown cut away in FIG. 3 in order to expose cylindrical carbon braid 22,which is covered by the sheath. In embodiments of the present invention,functional elements (e.g., electrode 64, position sensor 68, forcesensor 70, and any cabling) are within sheath 72 and run between adistal end 62 and a proximal end 74 of the probe. The functionalelements are typically constructed using non-magnetic materials. Usingnon-magnetic materials such as the platinum/iridium alloy describedsupra enables probe 60 to be MRI-compatible.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and subcombinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art.

The invention claimed is:
 1. A method comprising: passing a cylindricalcarbon fiber through a press so as to produce a flat ribbon; weavingmultiple strands of the flat ribbon together to create a flexiblecylindrical braid; cutting the flexible cylindrical braid to apre-defined cut length, thereby creating a section; covering the sectionwith a flexible biocompatible sheath; and positioning one or morefunctional elements within the cut length of the braid, therebyproducing a magnetic resonance imaging compatible medical probe.
 2. Themethod according to claim 1, wherein each of the one or more functionalelements is selected from a list consisting of an electrode, a positionsensor, a force sensor, cabling and tubing.
 3. The method according toclaim 1, wherein the magnetic resonance imaging compatible probecomprises only non-magnetic materials.